1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device, and a semiconductor device manufactured by the method.
2. Related Art
In electro-optic devices such as liquid crystal displays and organic EL displays, a transparent substrate made of inexpensive glass, resin or the like is used as a substrate. Since the substrate made of such a material has low heat resistance, semiconductor elements including thin-film transistors (TFTs) and various devices integrated on the substrate are normally manufactured by a low-temperature process (Refer, for example, to Japanese Patent No. 3528182).
There are generally strong demands for size reduction and density increase of semiconductor devices equipped with transistors and the like, to achieve a higher definition and so on of electro-optic devices on which the semiconductor devices are mounted for example.
However, in a transistor formed by a typical low-temperature process, the source and drain thereof are formed as an amorphous semiconductor layer because of impurity implantation into them. Therefore, especially in a transistor with a minute size, the parasitic resistance of the source and drain is too large to realize good electrical characteristics of the transistor.
It would also be possible to arrange semiconductor elements such as transistors three-dimensionally in order to achieve a higher density that offers a higher definition. However, when transistors and the like are manufactured on each of multiple semiconductor layers deposited on top of each other, high-temperature heat treatment performed for each layer for activating impurities gives semiconductor elements on other layers, a thermal history above the maximum temperature employed in normal process design for the semiconductor elements. This problem makes process design very difficult and complex, precluding use of e.g. a heat-sensitive salicide process.